PMDK Version 1.5.1

This release fixes minor bugs and improves compatibility with newer
tool chains.

Notable bug fixes:
- common: make detection of device-dax instances more robust
- obj: fix pmemobj_check for pools with some sizes
- obj: don't use anon struct in an union (public header)
- obj: fix pmemobj_tx_lock error handling
- obj: don't use braces in an expression with clang (public header)
- obj: suppress pmemcheck warnings for statistics
- pmreorder: fix markers nontype issue